The present invention relates to a semiconductor device using a compound semiconductor, such as a Schottky gate field effect transistor, and a method for the manufacture of the same.
Heretofore, metals such as aluminum(Al), gold(Au), titanium(Ti), molybdenum(Mo), tungsten(W), tantalum(Ta) and so forth have been employed, for example, for a gate electrode of GaAs Schottky gate field effect transistors. With any of these metals, however, when it is heat-treated at about 600.degree. C., the electrical properties of the gate electrode, such as, for example, the barrier height, the ideality factor and the reverse breakdown voltage are degraded, making the transistor operation impossible.
As a solution to this problem, it has recently been proposed to use a Ti/W alloy for the gate electrode.
But this alloy also cannot withstand, for example, a 800.degree. C. heat treatment, which results in a loss or degradation of the barrier to make the operation unstable. In addition to this, if an ordinary manufacturing process is adopted, the gate electrode may sometimes be corroded which increases its resistivity or causes it to flake off.